Purification of nickel matte with regenerated molten halide extractant

ABSTRACT

Molten nickel sulphide is refined by liquid-liquid extraction techniques. A bath of nickel matte containing chloridizable impurities is provided with a supernatant layer of a molten extractant consisting essentially of at least one chloride of a metal from Groups IA or IIA of the Periodic Table, and the bath is contacted with at least one reagent selected from the group consisting of chlorine and nickel chloride to chloridize chloridizable impurities which are collected in the molten extractant. The loaded extractant is treated to regenerate molten extractant which is recycled to chloridization step.

I United States Patent [111 3,802,870 Bell Apr. 9, 1974 [54] PURIFICATION OF NICKEL MATTE WITH 3,660,026 5/1972 Michel et a1 75/82 REGENERATED MO HALIDE 3,373,097 3/1968 Gomes et a1 75/1 1 1 3,704,113 11/1972 Hildreth 75/112 EXTRACTANT 3,622,302 1 1/1971 Hayashi et a1. 75/82 [75] Inventor; Malcolm Charles Evert Bell, Port 3,453,101 7/1969 Takahashi et a1 75/82 ColbO -ne Ontario Canada Maelzer et a1. [73] Assignee: The International Nickel Company, Primary Dewayne Rutledge New York Assistant Examiner-W. R. Satterfield [22] Filed: July 17, 1972 [57] ABSTRACT 21 A 1.N.:272,304 l 1 PP Molten nickel sulphlde 1S refined by liquid-liquid extraction techniques. A bath of nickel matte containing [30] Foreign Applic ion ri ri y Data chloridizable impurities is provided with a supernatant Aug. 20, 1971 Canada 121041 layer of a molten extractant consisting essentially of at least one chloride of a metal from Groups IA or 11A of [52] US. Cl 75/82, 75/63, 75/94 the Periodic Table, and the bath is contacted with at [51 Int. Cl C22b 23/00 least one reagent selected from the group consisting of [58] Field of Search 75/82, 93 F, 93 R, 93 A, chlorine and nickel chloride to chloridize chloridiza- 75/94, 112, 113, 111,63 ble impurities which are collected in the molten extractant. The loaded extractant is treated to regener- [56] References Cited ate molten extractant which is recycled to chloridiza- UNITED STATES PATENTS step- 3,069,254 12/1962 Queneau et a1 75/82 12 Claims, No Drawings PURIFICATION OF NICKEL MA'I'I'E WITH REGENERATED MOLTEN HALIDE EXTRACTANT The present invention pertains to refining nickel sulphide, and more particularly, to refining nickel sulphide by molten chloride liquid-liquid extraction techniques.

The recovery of nickel from sulphide ores containing both nickel and copper is often complicated by the presence of copper. The treatment of such ores most frequently involves pyrometallurgical operations in which the sulphides of nickel and copper are brought to a molten state. When the ore being treated is primarily a nickel ore, e.g., a nickel to copper ratio greater than about 5:1, it is highly desirable to refine molten nickel sulphide, but until recently no such process existed. With the exception of two processes described hereinafter, treatment of rich nickel sulphide melts invariably includes a solidification step prior to any treatment for copper removal. For example, molten nickel sulphide is cast into anodes and the nickel sulphide anodes are treated electrolytically to recover purified nickel and elemental sulphur. Or molten nickel sulphide is solidified, comminuted and thereafter treated to produce a refined nickel product. Most often, solidified nickel sulphide is roasted to produce nickel oxide and the nickel oxide is reduced for further purification by either electrorefining or by carbonylation. It has been recently suggested that solid nickel sulphide could be selectively chlorinated to chlorinate impurities, such as copper, and the selectively chlorinated impurities could be removed from the solid nickel sulphide by leaching. All these processes have the disadvantage of requiring an intermediate solidification step and are relatively slow when compared to the kinetics achieved when treating molten nickel sulphide.

Recently two processes have been proposed for removing copper sulphide from molten nickel sulphide. Queneau and Renzoni in US. Pat. No. 3,069,254 disclose a variation of the well known tops and bottoms process. The process disclosed in US. Pat. No. 3,069,254 involves contacting a molten solution of nickel and copper sulphide with a molten solution of sodium sulphide and sodium chloride or other alkali or alkaline earth chlorides to selectively dissolve copper sulphide and to provide purified nickel sulphide. Al-

though the process disclosed by Queneau and Renzoni is a substantial improvement over the prior art, the process is only capable of separating copper sulphide from nickel sulphide and other sulphides are substantially unaffected by the treatment. It has also been suggested that impure nickel sulphide be contacted with a slag containing nickel chloride and alkali or alkaline earth chlorides to purify the nickel sulphide. Slags, which are the reaction products between bases and silica, are characterized by relatively high fusion temperatures. In the extractive metallurgy of nickel, temperatures generally in excess of l,200C. are employed in order to insure that any slags employed remain fluid. Any process which requires incorporation of nickel chloride in a slag will be quite inefficient since nickel chloride sublimes at temperatures slightly above 1000C. (l832F.), well below the temperatures required by slags. ln any event, most slags can, even in the presence of alkali and/or alkaline earth chlorides, dissolve and retain only minor quantities of nickel chloride so that excess nickel chloride is vaporized therefrom. Nickel chloride volatilized from such slags will be oxidized rendering the process more inefficient. Another drawback of employing slags as a carrier for nickel chloride is that the recovery of nickel and impurities incorporated in the slag is quite difiicult. The presence of silica and bases in the slag increase the resistivity to such an extent that nickel chloride and impurity chlorides can not be electrolytically precipitated therefrom. Furthermore, the high temperatures employed in forming the slag along with the amorphous nature of the solidified slag renders the slag chemically inactive for other recovery processes, e.g., hydrometallurgical process. Moreover, the use of high temperatures which are dictated by the use of the slags as carriers for nickel chloride, create particularly corrosive conditions due to the presence of chlorine. Although attempts were made to overcome the foregoing difficulties and other disadvantages, none, as far as I am aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that nickel sulphide can be refined by use of a chloride extractant at only moderate temperatures and the molten extractant can be directly regenerated for re-use.

It is an object of the present invention to provide a process for refining nickel sulphide.

Another object of the present invention is to provide a process for removing copper from nickel sulphide in a molten state.

The invention also contemplates providing a pyrometallurgical liquid-liquid extraction process for refining molten nickel sulphide.

The invention further contemplates providing an overall process for refining nickel sulphide by a molten chloride liquid-liquid extraction technique and for recovering impurities and regenerating the molten chloride extractant for reuse.

Other objects and advantages will become apparent from the following description.

Generally speaking, the present invention contemplates a process for refining nickel sulphide. A bath of nickel sulphide containing chloridizable impurities is established, and the bath is provided with a molten supernatant layer of an extractant consisting essentially of at least one chloride of a metal from Groups IA or IIA of the Periodic Table. The bath is contacted with at least one reagent selected from the group consisting of nickel chloride and chlorine to chloridize the impurities, and the chloridized impurities are collected in the extractant to refine the bath to produce a loaded extractant. The loaded molten extractant is separated from the refined bath and is regenerated in the molten state for re-use.

Any material containing nickel sulphide, regardless of the manner in which it is produced, can be treated by the process in accordance with the present invention. However, for the sake of efficiency and overall operation, it is advantageous to treat a nickel sulphide material or nickel matte containing at least about 60 percent nickel, e.g., about percent or more nickel, and no more than about 26 percent sulphur, e.g., about 18 percent to about 24 percent sulphur, and a total chloridizable impurity content of no more than about 15 percent. The chloridizable impurity content advantageously should not exceed about 12 percent. As will be shown hereinafter, greater amounts of impurities are removed when the matte is sulphur deficient, i.e., the

sulphide contains less than about 2l percent sulphur, or less sulphur than is required to satisfy the stoichiometry of Ni S However, the sulphur deficiency should not be so great as to increase the melting point of the matte above about 900C., i.e., the sulphur content should not be less than about 18 percent, so that the liquid-liquid extraction can be conducted at a temperature between about 750C. and 900C. Chloridizible impurities which can be eliminated from nickel matte by processing in accordance with the present invention include, although the invention is not limited thereto, cadmium, cobalt, copper, iron, lead, manganese, tin and zinc. As noted hereinabove, these impurities advantageously are not present either individually or collectively in amounts exceeding about 12 percent since if present in greater amounts, larger and uneconomical amounts of the chloride extractant must be employed. Certain impurities can be lowered to less than about 1 percent by prior treatment, e.g., iron can be eliminated by blowing and slagging. When present in the foregoing amounts, the chloridizible impurities can, in most cases, be lowered in one or more stages to an amount of less than about 0.05 percent, e.g., the iron content can be lowered from initially about 1 percent to less than about 0.02 percent, cobalt from initially about 5 percent to less than about 0.02 percent, copper in nickel sulphide from initially about percent to less than about 0.02 percent, lead from initially about 0.25 percent to less than about 0.002 percent, cadmium from initially about 0.2 percent to less than about 0.005 percent, zinc from initially about 2.0 percent to less than about 0.5 percent, and tin from initially about 0.2 percent to about 0.01 percent. It will be noted that all compositions given herein are on a weight basis unless otherwise expressly stated.

As noted hereinbefore, nickel matte is refined by the process in accordance with the present invention at a temperature between about 750C. and 900C. Although temperatures higher than 900C. can be employed, high nickel losses are encountered due to the increase in the partial pressure of nickel chloride, and pressure or closed vessels must be used to minimize losses associated with these high partial pressures of nickel chloride. Higher temperatures also promote heat losses. Thus, in terms of reaction rates, chloride losses and heat consideration, it is advantageous to conduct the chloridizing treatment at a temperature between about 750C. and 900C.

An important feature of the present invention is the use of a supernatent molten chloride extractant for collecting the chloridized impurities. As will be shown hereinafter, the use of such an extractant renders the process more efficient, particularly when gaseous chlorine is employed as the chloridizing reagent. The extractant is at least one chloride of a metal from Groups [A or 11A of the Periodic Table, i.e., chlorides of alkali metal and alkaline earth metals. The extractant should have a melting point below about 800C. and a vapor pressure of no' greater than about 0.25 atmosphere at 800C. Of course, a combination of chlorides can be employed to provide an extractant having an even lower melting point. It is to be noted that for the purposes of this invention the term alkaline earth metal includes magnesium which forms a chloride that melts at 708C. and has a boiling point of 1,412C. From the physical standpoint, chlorides of sodium, potassium,

rubidium, magnesium and calcium can be employed individually whereas the chlorides of strontium and barium can only be employed in combination with at least one of the foregoing chlorides.

Another important characteristic which the chloride extractant must display is that it must be capable of dissolving nickel chloride as well as chloridized impurities. The chloride extractant should be capable of dissolving up to about l percent nickel chloride and even more advantageously, up to about 20 percent nickel chloride. For overall efficiency while minimizing nickel losses due to volatilization of nickel chloride, the chloride extractant contains between about 15 percent and 5 percent nickel chloride. If the chloride extractant does not dissolve nickel chloride, nickel chloride, which has substantial vapor pressures even at temperatures as low as 850C, is lost to the ambient atmosphere by volatilization from the system. Even more importantly, the absence of nickel chloride from the extractant system renders the process inoperative since there is no available nickel chloride to react with the impurities contained in the sulphide bath. For overall efficiency in removing a preponderant part of the impurities most commonly associated with nickel sulphide, it is advantageous to employ a molten chloride extractant containing equal amounts of sodium and potassium chlorides.

Chloridization of the impurities can be conducted in any manner that insures good liquid-liquid or gas-liquid contact, depending upon the state of the chloridizing reagent. When gaseous chlorine is employed as the chloridizing reagent, it is advantageously passed through the nickel matte in the form of tiny, well dis persed bubbles. For example, a suitable vessel can be equipped with one or more porous plugs through which the chlorine is passed thereby introducing the chlorine into the nickel matte in the form of small, well dispersed bubbles. However, when nickel chloride is employed as the chloridizing reagent, it is advantageously dissolved in the molten extractant, and good liquidliquid contact between the lower matte layer and the supernatant chloride extractant is insured by mixing either by mechanical, electromechanical or pneumatic agitation.

When chloridizing impurities in nickel matte by employing nickel chloride dissolved in the chloride extractant, the process can be conducted either on a batch or continuous basis. If conducted on a batch basis, one or more contacting operations can be employed. When it is desired to conduct the process on a continuous basis, countercurrent principles are advantageously employed. Equilibrium between the molten extractant and molten nickel matte is rapidly achieved. This fast rate of reaction is an important feature of the process, because it allows the use of a number of stages without requiring much additional heat at each stage. The process is advantageously conducted countercurrently in a tower arrangement. For example, molten impure nickel matte can be introduced at the top of a baffled tower while molten chloride extractant can be introduced at the bottom of the tower so that the flow of nickel matte in a downwardly direction and the flow of the molten extractant in the upwardly direction provide the desired countercurrent, liquid-liquid contact. Whether the molten nickel sulphide is treated on a batch basis or on a continuous basis, matte to extractant ratios of between about 2:1 and 1:3 are employed in order to insure that the nickel matte is refined to the desired extent. Lower sulphide to extractant ratios can be employed but such lower ratios create materials handling problems. Higher matte to extractant ratios can be employed but the matte will not be refined to the desired extent. The purified nickel sulphide can be treated by conventional methods to produce nickel or nickel oxide. Because molten nickel matte is highly refined by practice of the present invention, it is highly advantageous to surface blow turbulent molten matte with a free-oxygen-containing gas directly to nickel metal (oxygen nickel). After vacuum desulphurizing, deoxidizing, and degassing the nickel bath, the nickel can be cast, even on a continuous basis, to provide a nickel metal product which is suitable for most uses.

The loaded chloride extractant containing substantial quantities of nickel chloride and chlorides of the impurities is advantageously treated in the molten state to regenerate the chloride extractant and to recover nickel and valuable impurities. For example, the pregnant chloride extractant is transferred to an electrolytic cell which comprises a graphite container acting as a cathode and a graphite anode. Nickel and impurities are recovered as metallic alloy powders by electrolyzing the molten chloride extractant at a temperature between about 700C. and 900C. at an electricalpotential of about 1.5 volts to volts. Current densities of 1,000 amperes per square foot or even more can be employed but as the amount of metal powders produced increases, there is a noticeable decrease in current efficiency. Chlorine gas is evolved at the anode and is directly recycled to the chloridization operation or is used to produce nickel chloride, dissolved in the extractant. Upon completion of the electrolysis reaction, the regenerated extractant can be directly recycled for further use or can be treated to havenickel chloride added thereto before re-use as an extractant.

Advantageously, the loaded molten extractant is treated with magnesium or a magnesium base alloy to precipitate, by replacement reaction, nickel and the chlorinated impurities as a molten magnesium alloy. Magnesium or alloys thereof are added to the loaded extractant in amounts equivalent to between about 1 and 2 mole equivalents of magnesium for each mole equivalent of base metals in the loaded extractant. Since magnesium is less dense than is the chloride extractant, it is highly advantageous to employ a magnesium base alloy that contains at least about 6 percent nickel or copper. Best results are obtained by adding a magnesium base alloy containing between about 5 percent and 30 percent, e.g., between about 6 percent and percent nickel or copper. The magnesium alloy is advantageously added to the loaded extractant in particulate form while the extractant is maintained at a temperature between about 750C. and 900C. Although it is not absolutely necessary, it is highly advantageous to maintain the loaded chloride extractant in a turbulent state, by mechanical, electromechanical or pneumatic means, to facilitate reaction between the magnesium and the chloride extractant. The purified extractant can be recycled to the chloridization treatment while the alloy, containing nickel, cobalt, copper, iron and other impurities, can be treated to recover these elements. As the magnesium content of the chloride extractant continually increases it becomes advantageous to electrolytically treat the magnesium-laden extractant to recover the magnesium for further use.

Magnesium can be recovered from the extractant in electrolytic cells conventionally employed for recovering magnesium from magnesium chloride. The electrolytic treatment produces magnesium for purifying loaded extractant, a low magnesium salt and chlorine which can be recycled to the chloridization refining of nickel matte.

The magnesium-chloride-containing extractant can be either regenerated by passing chlorine, obtained as a byproduct of the electrolysis, through a portion of the refined matte that is provided with the supernatant molten chloride extractant layer, or the extraction process carried out directly by passing chlorine through the impure matte contacted with the supernatant molten chloride extractant. To insure rapid and efficient regeneration of the molten nickel-chloride-containing extractant, regeneration is conducted at a temperature between about 750C. and 800C., with the chlorine bubbling small bubbles through at least 10 inches of molten nickel sulphide.

For the purpose of giving those skilled in the art a better understanding of the invention, the following illustrative examples are given:

EXAMPLE 1 Impure nickel matte containing 26.4 percent sulphur, 0.65 percent copper, 0.78 percent cobalt and the balance essentially nickel was heated to a temperature of 780C. and was contacted with molten sodium chloride containing 10 percent nickel chloride. The reaction between the molten chloride extractant and the nickel matte was conducted on a batch basis, and the ratio of nickel matte to chloride extractant was about 1:1. The final matte analyzed 0.2 percent copper, 0.1 percent cobalt, and 72.6 percent nickel. The liquid chloride extractant had a final analysis of 0.4 percent copper, 0.46 percent cobalt and 1.90 percent nickel. The nickel, cobalt and copper contained in the loaded extractant were recovered from the extractant as an alloy powder by electrolysis in a manner similar to that disclosed in Example Vlll.

EXAMPLE II This example confirms that mattes more deficient in sulphur are refined to a greater extent than mattes containing greater amounts of sulphur. The analyses of the nickel mattes are given in Table I. Molten nickel mattes were contacted with liquid sodium chloride containing 10 percent nickel chloride at 780C. on a batch basis. Ratios of nickel matte to chloride extractant of 2:1 were employed. The final analyses of the nickel mattes and the chloride extractants are also given in Table I. It is noted from Table 1 that the final copper and cobalt analyses were lower in matte B, the more sulphur deficient matte. The loaded extractants were treated ina manner similar to that shown in Example Vlll to electrically precipitate an alloy powder containing nickel, cobalt and copper.

TABLE l-Continued iron ratio from about 50:1 to about 90001. The loadedextractant was electrolyzed as described in Example Test A Cu Co i; Ni Vlll to precipitate an alloy powder and to regenerate Test B Cu Co s Ni the extl'actamiiiiii sii il 3123 (iii & EXAMPLE v Loaded Extractant 0.64 0.77 2.76

This example confirms the importance of maintain- 10 ing a supernatant chloride extractant on the surface of the molten matte during the chloridization treatment. EXAMPLE A nickel matte sample having the composition given in This example confirms the effectiveness of counterab e Ill as provided with a supernatant layer of a curl-em extracticn Ni k l matte n i i 26,6 chloride extractant containing equal proportions of socent sulphur, 0.87 percent copper, 1.01 percent cobalt dium chloride and potassium chloride. The matte to exand 0.22 percent iron and the balance essentially, nickel tractam ratio Was The matte n e Sample ere was contacted with a chloride extractant consisting of maintained at a temperature of and gaseous sodium chloride with 10 percent nickel chloride at o ine at a rate of 0.4 liter per minute per kilogram 780C. with a ratio of matte to chloride extractant of f mat e Was passed through the nickel matte for 2 2:1. After the first stage extraction the matte contained hours. The final matte and the loaded extractant had 0.5 percent copper, 0.3 percent cobalt, 0.026 percent the compositions given in Table 111. Another nickel iron and 72.1 percent nickel and after second stage exmatte having the composition given in Table IV was traction the matte analyzed 0.25 percent copper, 0.8 -maintained at 930C. while gaseous chlorine was percent cobalt, 0.01 percent iron and 72.8 percent passed therethrough at a rate of 0.4 liter per minute per nickel. The first stage chloride extractant contained kilogram of matte for 2 hours. The refined matte had 0.83 percent copper, 0.01 percent cobalt, 0.22 percent a composition given in Table IV. By comparing the reiron, and 2.7 percent nickel while the second stage exfined matte compositions given in Tables Ill and 1V it tractant contained 0.48 percent copper, 0.37 percent is apparent that nickel matte is more thoroughly recobalt, 0.045 percent iron, and 3.19 percent nickel. fined by employing a supernatant layer of a chloride ex- Thus, between the first stage and the second stage of tractant. Thus, in order to fully realize all the benefits extractions the nickel to copper ratio in the matte was flowing from the chloridizing treatment it is essential to increased from about 144:1 to about 290:1. The nickel provide an effective molten chloride extractant as well to cobalt ratio in the matte was increased from about as means for economically regenerating such extract- 180:1 to about 900:1 and the nickel to iron ratio in the ant. The loaded chloride extractant was treated in a matte was increased from about 280011 to about manner similar to that described in Example Vlll to 7300:1. A nickel-copper-cobalt-iron alloy powder was precipitate a nickel-copper-cobalt-iron alloy powder precipitated from the loaded extractant in a manner and to regenerate the chloride extractant. similar to that described in Example V111, and the ex- TABLE "I tractant was regenerated for subsequent re-use.

EXAMPLE 1v 40 ma %Cu %Ni %Co %Fe %S This example confirms the improved results obtained by employing sulphur deficient nickel matte, countergig 8:3; 3:5: 5; current princlples and low mckel matte to extractant Fina; 055 ratios. Nickel sulphide containing 20 percent sulphur, 0.8 percent copper, 0.78 percent cobalt, 0.38 percent iron and the balance essentially nickel was contacted in TABLE IV three countercurrent stages with a chloride extractant consisting of sodium chloride and 10 percent nickel Amy: chloride at 780C. The total amount of chloride ex- %Cu Ni Co Fe s tractant employed was such that an overall matte to H chloride extractant ratio of 1:! was employed. The final 8g? 32:; gig 31%: 31; analyses of the matte and the chloride extractant are given in Table II. It is seen from these results that between the initial matte and the final nickel sulphide, the nickel to copper ratio was increased from :1 to EXAMPLE VI a u 5 the nickel to c alt ratio a n as d A two-stage matte refining process is shown by this TABLE 11 Analysis Nickel Sulfide Extractant Stage Cu Co Fe Cu Co Fe Ni Initial 0.8 0.78 0.38

. Sulfide is! 0.24 0.067 0.016 0.75 0.57 0.13 3.58 2110 0.087 0.008 0.028 0.19 0.068 0.04 2.0 3rd 0.016 0.004 0.009 0.047 0.013 0.032 4.4

example. A nickel matte having the composition given in Table V was provided with a supernatant layer of a chloride extractant containing equal amounts of sodium chloride and potassium chloride. The matte to extractant ratio was 3:5. The matte and supernatant extractant layer were maintained at a temperature of 815C. and gaseous chlorine at a rate of 0.4 liter per minute per kilogram of matte was passed through the nickel matte for 2 hours. The final matte and loaded extractant of this first stage refining had the analyses shown in Table V. After the loaded extractant from the first stage refining was separated from the nickel matte, the nickel matte was provided with an equal amount of supernatant chloride extractant layer containing equal amounts of sodium chloride and potassium chloride. While maintaining the matte and the extractant at a temperature of 815C, gaseous chlorine at a rate of 0.4 liter per minute per kilogram of matte was again passed through the nickel matte for 2 hours. The analyses of the loaded extractant and the refined matte are given in Table VI. It is apparent from Table VI that multistage treatments are quite effective in producing highly refined nickel mattes. The loaded chloride extractant for each refining stage was regenerated in a manner similar to that described in Example VIII, and a nickelcopper-cobalt-iron alloy powder was recovered from the electrolytic treatment.

EXAMPLE VII This example confirms the effectiveness of a chloridizing treatment in removing impurities other than cobalt, copper and iron. Nickel matte containing cadmium, lead, tin and zinc in the amounts shown in Table V11 was treated at 810C. with a chloride extractant containing equal amounts of sodium chloride and potassium chloride and 12 percent nickel chloride with the matte to extractant ratio being 1:1.5. The compositions of the refined matte and the loaded extractant are given in Table VII. The loaded extractant, after being separated from the refined matte, was electrolyzed in a manner similar to that described in Example V111 to produce an alloy powder containing nickel, lead, tin,

EXAMPLE VIII This example confirms that loaded chloride extractant can be electrolyzed to produce alloy powders and to regenerate the chloride extractant for further re-use. An electrolytic bath containing 40 grams of sodium chloride and 40 grams of potassium chloride and containing copper, nickel, cobalt and iron in the amounts shown in Table V111 was established and maintained at a temperature of 800C. A two volt potential difference was impressed upon graphite electrodes immersed in the loaded extractant, and an anode current density of 83 amperes per square decimeter was maintained. After 32 minutes at least about percent of the copper, nickel, cobalt and iron were precipitated from the loaded extractant at the cathode while chlorine was evolved at the anode; and the regenerated extractant, the analyses of which is given in Table V111, was suitable for re-use in the chloridizing treatment. Under these conditions a current efficiency of 51 percent was realized.

This example shows the electrolysis of a loaded extractant on a larger scale, an electrolytic bath containing 5,000 grams of sodium chloride and 5,000 grams of potassium chloride and containing copper, nickel, cobalt and iron in the amounts shown in Table IX was established and maintained at a temperature of 780C. A stainless steel cathode and a graphite anode were immersed in the electrolytic bath and a potential difference of two volts was impressed upon the electrodes. The anode current density was 60 amperes per square decimeter while the cathode current density was 93 amperes per square decimeter. After a period of 6 hours, at least about 95 percent of the copper, nickel and cobalt were precipitated from the loaded extractant at a current efficiencyof 53 percent. The regenerated extractant having the composition given in Table IX was suitable for recycling to the chloridizing treatment and the chlorine evolved at the anode was recycled to the chloridizing treatment to chloridize further impurities in the nickel matte.

TABLE IX Analysis Cu Ni Co Fe Initial Salt 10,000 gm. 2.95 1.45 0.14 0.40 Final Salt 0.02 0.01 0.013 0.05

EXAMPLE X This example demonstrates that a loaded chloride extractant can be regenerated by the addition of a magnesium base alloy. A particulate magnesium base alloy, having the composition given in Table X, was introduced in an amount one mole equivalent of magnesium for each mole equivalent of base metal in the loaded extractant, which comprises equal parts of sodium and potassium chlorides and which contained chloridized metal values in the amounts shown in Table X. The loaded extractant was at a temperature of 750C. when the magnesium alloy was added thereto, and was maintained in an agitated state to provide good liquid-liquid contact between the liquid magnesium alloy and the supernatant loaded extractant. The regenerated extract- Balance magnesium plus limited amounts of oxygen combined with the magnesium.

EXAMPLE X] This example demonstrates the cyclic nature of the process in accordance with the present invention. A loaded extractant, having the composition shown in Table XI and at a temperature of 750C., was reacted with a magnesium base alloy having the composition given in Table XI, in an amount of about one part of magnesium base alloy for each l7 parts of loaded extractant in a manner similar to that described in Example X. The regenerated extractant had the analyses given in Table XI.

Molten nickel matte, having the composition given in Table Xll and at a temperature of 750C, was treated with gaseous chlorine in the manner described in Example ll to produce a refined matte showing the analyses given in Table Xll. During the chlorination treatment, the nickel matte was provided with a supernatant layer of the regenerated extractant in an amount equivalent to about three parts of extractant for each five parts of matte to collect the chlorinated impurities. The analyses of the regenerated and the loaded extractant are also given in Table Xll. This example confirms that the process can be conducted on a cyclic basis thereby minimizing reagent and fuel costs.

TABLE XII-Continued %lVlg Loaded extractant Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations can be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention.

I claim 1. A process for refining nickel sulphide by chloridization including treatment of an extractant used in the chloridization process which comprises: establishing a bath of nickel sulphide containing between about 18 percent and 26 percent sulphur and at least one chloridizable impurity selected from the group consisting of cadmium, cobalt, copper, iron, lead, manganese,'tin, and zinc in a total amount up to about l5%; providing the bath with a supernatant layer of a molten extractant consisting essentially of at least one chloride of a metal from Groups lA or IIA of the Periodic Table; contacting the bath with at least one reagent selected from the group consisting of nickel chloride dissolvedin the molten extractant to provide the molten extractant with a nickel chloride concentration between about 0.1 percent and 20 percent or gaseous chlorine to chloridize the chloridizable impurity, to collect the chloridized impurity in the molten extractant, and to produce refined nickel sulphide, separating the molten extractant containing the chloridized impurity from the refined bath; and electrolyzing the molten extractant containing the chloridized impurity to precipitate an alloy of nickel and the impurity, to produce gaseous chlorine, and to regenerate the molten extractant for re-use in the chloridizing step.

2. The process described in claim 1 wherein nickel chloride is added to the regenerated molten extractant which is then recycled to the chloridization step.

3. The process as described in claim 1 wherein the regenerated molten extractant is contacted with refined nickel sulphide and gaseous chlorine is passed therethrough to provide the molten extractant with a nickel chloride concentration between about 0.1 percent and 20 percent.

4. The process described in claim 1 wherein the regenerated molten extractant is recycled directly to the bath of impure nickel sulphide and chlorine is passed therethrough to chloridize nickel and the impurity in the bath thereby refining the nickel sulphide and collecting the chloridized impurity in the molten extractant.

5. The process described in claim 1 wherein the loaded extractant is electrolytically treated at a temperature between about 750C. and 900C.

6. A process for refining nickel sulphide by chloridization including treatment of an extractant used in the chloridization process which comprises:v establishing a bath of nickel sulphide containing between about 18% and 26 percent sulphur and at least one chloridizable impurity selected from the group consisting of cadmium, cobalt, copper, iron, lead, manganese, tin, and zinc in a total amount up to about 15%; providing the bath with a supernatant layer of a molten extractant consisting essentially of at least one chloride of a metal from Groups IA or lIA of the Periodic Table; contacting the bath with at least one reagent selected from the group consisting of nickel chloride dissolved in the molten extractant to provide the molten extractant with a nickel chloride concentration between about 0.1 percent and percent or gaseous chlorine to chloridize the chloridizable impurity, to collect the chloridized impurity in the molten extractant, and to produce refined nickel sulphide; separating the molten extractant containing the chloridized impurity from the refined bath; and adding at least one metal selected from the group consisting of magnesium or magnesium base alloys to precipitate the chloridized impurity from the molten extractant to regenerate the molten extractant for re-use in the chloridizing step.

7. The process described in claim 6 wherein the molten extractant containing the chloridized impurity is treated with a magnesium base alloy containing at least about 6% nickel or copper so that the alloy sinks in the molten extractant thereby minimizing oxidation of the alloy.

8. The process described in claim 7 wherein the magnesium base alloy contains between about 6 percent and 30 percent nickel or copper.

9. The process described in claim 6 wherein at least a portion of the magnesium-laden molten extractant is electrolytically treated to recover magnesium, to regenerate the molten extractant and to produce chlorine which is recycled to the refining operation.

10. The process described in claim 6 wherein nickel chloride is added to the molten extractant to provide the extractant with a nickel chloride concentration between about O.1 percent and 20 percent which is then recycled to the chloridizing step.

11. The process as described in claim 6 wherein the regenerated molten extractant is contacted with refined nickel sulphide and gaseous chlorine is passed therethrough to provide the molten extractant with a nickel chloride concentration between about 0.1 percent and 20 percent for re-use in the chloridizing step.

12. The process described in claim 6 wherein the regenerated molten extractant is recycled directly to the bath of impure nickel sulphide and gaseous chlorine is passed therethrough to chloridize nickel and the impurity in the bath thereby refining the nickel sulphide and collecting the chloridized impurity in the molten extractant. 

2. The process described in claim 1 wherein nickel chloride is added to the regenerated molten extractant which is then recycled to the chloridization step.
 3. The process as described in claim 1 wherein the regenerated molten extractant is contacted with refined nickel sulphide and gaseous chlorine is passed therethrough to provide the molten extractant with a nickel chloride concentration between about 0.1 percent and 20 percent.
 4. The process described in claim 1 wherein the regenerated molten extractant is recycled directly to the bath of impure nickel sulphide and chlorine is passed therethrough to chloridize nickel and the impurity in the bath thereby refining the nickel sulphide and collectIng the chloridized impurity in the molten extractant.
 5. The process described in claim 1 wherein the loaded extractant is electrolytically treated at a temperature between about 750*C. and 900*C.
 6. A process for refining nickel sulphide by chloridization including treatment of an extractant used in the chloridization process which comprises: establishing a bath of nickel sulphide containing between about 18% and 26 percent sulphur and at least one chloridizable impurity selected from the group consisting of cadmium, cobalt, copper, iron, lead, manganese, tin, and zinc in a total amount up to about 15%; providing the bath with a supernatant layer of a molten extractant consisting essentially of at least one chloride of a metal from Groups IA or IIA of the Periodic Table; contacting the bath with at least one reagent selected from the group consisting of nickel chloride dissolved in the molten extractant to provide the molten extractant with a nickel chloride concentration between about 0.1 percent and 20 percent or gaseous chlorine to chloridize the chloridizable impurity, to collect the chloridized impurity in the molten extractant, and to produce refined nickel sulphide; separating the molten extractant containing the chloridized impurity from the refined bath; and adding at least one metal selected from the group consisting of magnesium or magnesium base alloys to precipitate the chloridized impurity from the molten extractant to regenerate the molten extractant for re-use in the chloridizing step.
 7. The process described in claim 6 wherein the molten extractant containing the chloridized impurity is treated with a magnesium base alloy containing at least about 6% nickel or copper so that the alloy sinks in the molten extractant thereby minimizing oxidation of the alloy.
 8. The process described in claim 7 wherein the magnesium base alloy contains between about 6 percent and 30 percent nickel or copper.
 9. The process described in claim 6 wherein at least a portion of the magnesium-laden molten extractant is electrolytically treated to recover magnesium, to regenerate the molten extractant and to produce chlorine which is recycled to the refining operation.
 10. The process described in claim 6 wherein nickel chloride is added to the molten extractant to provide the extractant with a nickel chloride concentration between about 0.1 percent and 20 percent which is then recycled to the chloridizing step.
 11. The process as described in claim 6 wherein the regenerated molten extractant is contacted with refined nickel sulphide and gaseous chlorine is passed therethrough to provide the molten extractant with a nickel chloride concentration between about 0.1 percent and 20 percent for re-use in the chloridizing step.
 12. The process described in claim 6 wherein the regenerated molten extractant is recycled directly to the bath of impure nickel sulphide and gaseous chlorine is passed therethrough to chloridize nickel and the impurity in the bath thereby refining the nickel sulphide and collecting the chloridized impurity in the molten extractant. 